Long-distance electricity transmission is typically carried with high voltage conductors. Transmission at higher voltages reduces resistance power loss, therefore line voltage for long distance lines is stepped up after generation by passing it through transformer stations prior to feeding the power to long-distance transmission lines. Transmission lines traverse large regions and require numerous support towers. The conductors in high tension power lines are typically uninsulated because of the cost and additional weight of insulated versus uninsulated conductors.
Electric poles, towers, and other electrical equipment including substations provide attractive roosts for birds, particularly in treeless regions. If the wings of a bird simultaneously contact a conductor and another object such as an adjacent conductor, support tower or tree, the resulting electrical short-circuit can kill the bird and also damage the power system. The electrical short can further cause electrical system damage resulting in power outages. Because large (and typically protected) birds are more susceptible to such incidental contact, electrocution hazards disproportionately affect large bird species such as raptors.
Substations transform power from transmission voltages to distribution voltages (typically ranging from 2400 volts to 37,500 volts). Distribution voltages allow for reduced system clearances. These reduced clearances between phase to ground and phase to phase, increase station susceptibility to bird or animal caused outages. Faults caused by birds and other animals often trigger sensitive relay protection schemes, resulting in substation lockouts, interrupting service to thousands or possibly tens of thousands of customers and at the same time damaging expensive substation equipment.
Thus, in the field of electrical power transmission and distribution there is a need to insulate electrical power systems from short circuits caused by birds and other animals. The variety and number of proposed solutions for repelling birds and other animals from electrocution risks highlights the persistence and magnitude of the problems created by such undesirable intrusion. Many different types of scarecrows and other moving devices have been developed to repel birds. In addition to moving devices, various physical structures often involving spikes or other physical barriers, have been developed to discourage birds from roosting on structures. Other bird repelling concepts use electricity or magnetic fields to discourage bird intrusion. Equipment shield and cage devices have been specifically designed to block birds and other animals from accessing and short-circuiting electrical leads, such as described in U.S. Pat. Nos. 5,153,383 and 5,485,307.
The inventor's own prior patent document discloses protectors for components of electrical power transmission systems, see United States patent publication no. 20080123254, as well as methods of making such protectors. These covers are made by spray molding dielectric materials. However, the process of making and installing these components can be costly. Firstly, in order to make a suitable mold for such a cover, accurate measurements must be made of the component itself. This involves taking a physical measurement that requires an on-site visit and usually a power-down of the electrical system, both of which add to the cost of producing the covers and protecting the electrical equipment.
Power downs for the purpose of measuring electrical equipment for protective covers can keep a system down for a half a day or longer time period, at great cost. Some systems are operated under the direction of a regulatory and scheduling authority that controls the system's downtime scheduling. In locations with minimal spare power transmission capacity, it can be a challenge for a system to get the downtime needed to measure its equipment.
Making accurate hands-on measurement of power equipment for close-fitting protective covers requires training and skill. Because electrical systems are usually scheduled for maintenance downtime on a fairly short notice (typically a week for non-emergency situations), and because scheduled downtime may be cancelled by the Regulatory Authority on an extremely short notice, there is no guarantee that a suitable expert will be available to take the required measurements during a system's available downtime period. As a result, a system can experience significant delays in protecting their equipment.
Further, electricity transmission systems are built using components made by a number of different manufacturers assembled in an almost infinite variety of configurations, creating variations in final system dimensions from site to site, such that in many cases custom molds are required in order to create a suitable cover. It is possible to reduce the cost associated with protecting such electrical systems by using a generic mold to make an approximately suitable cover for each component, but the end result is typically a looser-fitting and hence less effective cover.
Thus, there is a need for methods that reduce the costs of producing and installing effective, close-fitted covers. Specifically, there is a need for a method of accurately determining the dimensions of electrical equipment to allow measurements to be obtained from energized equipment by a person positioned outside the Limits of Approach.